Conventionally, such a lever type traction machine has been proposed, which as disclosed in, for example, the Japanese Utility Model Publication Gazette No. Hei 2-6065 and shown in FIG. 5, is so constructed that a load sheave A engageable with a chain B is rotatably interposed between side plates; an operating lever is operated to drive a driving shaft S directly connected to or in association with the load sheave A through a speed reduction mechanism so as to haul the chain B engaged with the load sheave A, and a pair of chain holders, C1 and C2 are provided between the side plates, at both radial sides of the load sheave A for guiding therebetween the entering chain B to load sheave A.
The chain holders C1 and C2 in the lever type traction machine, as shown in FIG. 5, each form a guide surface in a circular arc at the opposite surface to the load sheave A, and the guide surface is formed in a circular arc around the center apart from the guide surface with respect to the axis of the driving shaft so that the chain B entering between the side plates can be guided toward the load sheave A.
At both side surfaces of the respective chain holders C1 and C2 are provided circular projections to be fitted into fitting bores provided at the side plates, respectively. Insertion bores F are also provided for receiving stay bolts E for fixing the side plates, respectively. The stay bolts E are screwably tightened by nuts so as to fixedly maintain each chain holder C1 or C2 between the side plates at the two positions of the projection D and stay bolt E.
In the lever type traction machine constructed as above, the guide surface at each chain holder C1 or C2 is formed in a circular arc and a wide forward gap is provided between the guide surface and the load sheave A in the entering direction of the chain, whereby the chain B can properly be guided, so as to enter between the side plates toward the load sheave A and prevented from rising with respect to the load sheave A at the portion of a smaller gap. However, the guide surface of each chain holder C1 or C2 similarly is formed in a circular arc which is wide rearwardly in the entering direction, whereby, when the chain is hauled, the load sheave is free-rotatably controlled so as to adjust the chain in length as discussed below, or load traction is released in the state where the lever type traction machine is turned sidewise or upside down. That is, in the state where the drawing plane in FIG. 5 is turned upside down, the chain B engaging with the load sheave A may be swollen (slackened) due to gravity rearwardly in the entering direction of the chain B with respect to each chain holder C1 or C2. Such a swollen chain B interferes with the stay bolt E, or links of the chain B become intertwined with each other, thereby creating the problem in that the load sheave A is hindered from being smoothly driven.
The traction machine, usually, makes the load sheave freely rotatable in the traction direction or the traction releasing direction as the above-mentioned, but since the guide surface of each holder C1 or C2 is formed in a circular arc, when the chain B is intensively hauled in the twisted condition during the free rotation operation, the chain B may enter between each chain holder C1 or C2 and the load sheave. As the result, a problem is created in that the chain B is caught by the chain holder C1 or C2, thus locking the free rotation of the load sheave A.
The chain holders C1 and C2 each fit the fitting projection D into the round fitting bore at each side plate and insert the stay bolt E into the insertion bore F, so as to be fixedly sandwiched between the side plates while being locked at the two positions of the projection D and stay bolt E. Hence, the chain holders C1 and C2 must be constructed to form thereon the insertion bores F, other than projections D, so as to be complicated in construction and requiring much time for machining. Also, the chain holders are large-sized and heavy due to the formation of the insertion bores F. Moreover, the chain holders C1 and C2, when fixedly placed between the side plates, require much time to insert the stay bolts E into the insertion bores F, respectively, thereby creating the problem in that the assembly is complicated.